Comment 2 for bug 1742378

Produces this output:

$ sh check_power_test.sh
+ echo begin
begin
+ check_power 0
+ exit 0
+ return 0
+ check_power 1
+ exit 1
+ [ 1 -ne 1 ]
+ return 1
+ echo ignore
ignore
+ check_power 255
+ exit 255
+ [ 255 -ne 1 ]
+ return 0
+ echo end
end